Direction indicator control circuit

ABSTRACT

A direction indicator control circuit for a vehicle has a manually operable switch biased open and an electromagnetic bistable latching arrangement which is operated when the switch is closed momentarily. The latching arrangement closes a contact coupling a flasher unit to a flasher lamp, and a further momentary closure of the switch will operate the latching mechanism again to open the contact. When a turn has been negotiated the latching mechanism is operated to open the contact.

United States Patent Holt 5] Dec. 9, 1975 DIRECTION INDICATOR CONTROL 3.588,812 6/1971 Wheelock 340/73 x CIRCUIT [75] inventor: William David Holt, Colne, England P i Examiner-Donald J. Yusko [73] Assignee: Lucas Electrical Company Limited, Attorney Agent Firm-Holman & Stem Birmingham, England [22] Filed: May 20, 1974 [57] S C [211 App]. No.: 471,716

A direction indicator control circuit for a vehicle has [30] Foreign Application Priority Data a manually operable switch biased open and an elec- Ma 1 9 1973 United Kin dom 23961, tromagnetic bistable latching arrangement which is y g operated when the switch is closed momentarily. The latching arrangement 'closes a contact coupling a (5 figfhit gz flasher unit to a flasher lamp, and a further momen- [58] Fieid /73q55 80q8l R tary closure of the switch'will operate the latching lsl F, a i 5 mechanism again to open the contact. When a turn has been negotiated the latching mechanism is oper- [56] Reierences Cited ated to open the contact.

UNITED STATES PATENTS 4 Claims 1 Drawing Figure 3,308,428 3/1967 Grontkowski 340/81 R go 122 m 119 11 157 1210 131 1110 a 103 A'AvA L 152 1287 :2 10g al l i L/HOG U.S. Patent Dec. 9, 1975 DIRECTION INDICATOR CONTROL CIRCUIT This invention relates to direction indicator control circuits for road vehicles.

A circuit according to the invention includes a manually operable switch biased to an open position, an electromagnetic bistable latching mechanism which is operated when the switch is closed momentarily and serves to close a contact coupling a flasher unit to a flasher lamp, a further momentary closure of the switch serving to operate the latching mechanism again to open the contact, and means operable upon completion of a turn for operating the latching mechanism to open the contact. I

The accompanying drawing is a circuit diagram illustrating diagrammatically part of one example of the invention.

Referring to the drawing, there are provided positive and negative supply lines 101, 102, the line 102 being earthed and the line 101 being connected to the battery of a road vehicle either directly or through the ignition switch of the vehicle.

The circuit further includes a permanent magnet latching relay having a winding 103 and three contacts 104, 105, 106. If the winding 103 is energised by connecting its lower end to a positive supply line and its upper end to earth, then it moves the contacts from the positions shown to their alternative positions, and the contacts are held in their alternative positions by the permanent magnet, even when the winding 103 is deenergized. If the winding 103 is then energised again, this time by connecting its upper end to the positive supply and its lower end to earth, the contacts 104, 105, 106 are moved back to the positions shown. The position of the contacts 104, 105, 106 indicated in the drawing will be referred to as the normal position, and the alternative position as the energised position.

The contact 106 serves when in its energised position to complete a circuit between the lines 101, 102, the circuit including a flasher unit 107 and the direction indicator lamps 108 on one side of the vehicle. Connected in parallel with the lamps 108 is a pilot lamp 109 which flashes at the same time as the lamps 108. The contact 105 serves in its normal position to connect the upper end of the winding 103 to the line 102 through a manually operable push button switch 110, and when the contact 105 is in its energised position it connects the lower end of the winding 103 to the line 102 through the switch 110. Moreover, the upper and lower ends of the winding 103 are connected to the line 101 through capacitors 111, 112 respectively, the capacitors 111, 112 being bridged by resistors 113, 114 respectively.

The vehicle includes a steering column indicated diagrammatically at 116, and on the steering column is a permanent magnet 117. When the vehicle negotiates a lefthand turn, the magnet 117 closes a pair of reed switches 118, 119, in turn. The contact 104 when in its energised position completes a circuit from the line 101 by way of the contact 104, the switch 119 and a diode 121 to a supply line 122 which is coupled to the line 102 through a capacitor 123. The line 122 is connected to the collectors of a pair of transistors 124, 125

through resistors 120, 127 respectively, the emitters of the transistors 124, 145 being connected to the line 102. The bases of the transistors 124, 125 are connected to the collectors of the transistors 125, 124

through resistors 126, 127 respectively,.and the base of the transistor 125 isconnected to the line 102 through a capacitor 128 and the switch 118 in series. The ca- The circuit thus far described is associated only with the left-hand side of the vehicle, and an equivalent set of components are associated with the right-hand side of the vehicle. The equivalent reed switches 118a and 1 19a are seen in the drawing, as is the equivalent switch 110a which is pressed when a right-hand turn is to be negotiated.

in operation, when a left-hand turn is to be negotiated the drive momentarily presses the switch 110, and current flows by way of the contact to charge the capacitor 111 rapidly, and to'charge the capacitor 112 by way of the winding 103, thereby energising the winding 103. Energisation of the winding 103 moves the contacts 104, 105, 106 to their energised positions, and as previously explained the contacts remain in their energised positions after the switch is opened. As soon as the switch 106 is in its energised position, the flasher unit 107 operates to cause flashing of the lamps 108.

As a turn is negotiated, then assuming that the steering wheel is moved far enough, the sequences that the switch 118 closes, then the switch 119 closes with the switch 118 still closed, then the switch 118 opens but the switch 119 remains closed, and finally the switches 118, 119 both open. After the turn is completed and the steering wheel is moved in the opposite direction, the opposite sequence takes place. It will be seen that as the turn is negotiated, closing of the switch 118 has no effect because the line 122 is not connected to a source of supply. When the contact 119 closes, the line 122 is connected by way of the switch 119 and the contact 104 to the line 101, so that the capacitor 130 charges through the resistors 127, 126, and the capacitor 128 charges by way of the resistors 120, 127 and the switch 118. The components are so selected that the capacitor 128 becomes charged before the capacitor 130, and when the capacitor 128 is charged, the transistor 125 turns on so that when the capacitor is charged, the transistor 124 does not turn on because of the normal action of the bistable circuit. Further movement of the steering wheel opens contact 118, and then contact 119, and the capacitor 130 discharges through the base-emitter of the transistor 124, and the capacitor 128 discharges through the resistor 129.

When the turn has been negotiated and the steering wheel is moved back towards its normal position, the switch 119 closes and the capacitor 130 charges. The capacitor 128 does not charge because the switch 118 is open. Because the capacitor 130 is charging, the transistor 124 is off, and current flowing through the resistors 120, 127 turns on the transistor 125, so that once the capacitor 130 has charged, the bistable action holds off the transistor 124. Further movement of the steering wheel closes the switch 118 as well as the switch 119, and now the capacitor 128 can charge. Charging of the capacitor 128 reduces the base potential of the transistor 125, and so the circuit switch is to its alternative state with the transistor 124 on and the.

transistor 125 off. The transistors 131, 132, which previously were held off by virtue of conduction of the transistor 125, now turn on, and the lower end of the winding 103 is connected through the transistor 132 to earth. The capacitor 111 now charges rapidly, and the capacitor 112 charges through the winding 103, moving the contacts I04, 105, 106 to their normal positions so that the flasher unit 107 no longer operates. Thus, the overall action of the bistable circuit is to ensure that the transistors 131, 132 remain off until the switch 118 closes on the return movement of the steering wheel. As the turn is being negotiated, the transistors 131, 132 are held off initially by virtue of the capacitor 130, which when it is charging removes base current from the transistors 13], I32, and then later the conduction of the transistor I25 holds off the transistors 131, 132. On the return movement, the transistor 125 again conducts to hold off the transistors 13], 132, and finally the transistor 125 is turned off, and at this stage the capacitor [30 is charged so that base current can flow through the resistor 127 to the transistors 13], 132.

When the flasher unit is operating, it can be cancelled by the driver by pressing the switch 110 again. Closing of the switch 110 has exactly the same effect as conduction of the transistors 131 and 132, because it connects the upper end of the winding 103 to the line 102. This provision is particularly useful when a driver is changing lanes, because the movement of the steering wheel may then not be sufficient to close the switches 118, 119.

Provision is also made for stopping operation of the flasher unit 107 if the other switch 1100 is pressed at any time. For this purpose, a diode 120 is provided for connecting the upper end of the winding 103 to the line 102 by way of the switch 110a. An equivalent diode 12011 is provided for de-energising the flasher unit associated with the right-hand circuits of the vehicle whenever the switch is closed.

I claim:

1. A direction indicator control circuit for a road vehicle, including a manually operable switch biased to an open position, an electromagnetic bistable latching mechanism which is operated when the switch is closed momentarily and serves to close a contact coupling a flasher unit to a flasher lamp, a further momentary closure of the switch serving to operate the latching mechanism again to open the contact, and means operable upon completion of a turn for operating the latching mechanism to open the contact.

2. A circuit as claimed in claim 1 in which said means is magnetically operable.

3. A circuit as claimed in claim 2 in which the magnetically operable means operates a bistable circuit which in turn operates the latching mechanism.

4. A circuit as claimed in claim 3 in which the magnetically operable means includes first and second normally open switches operated by a permanent magnet on the steering column of the vehicle, movement of the steering column to negotiate a turn serving in sequence to close the first switch alone, then the first and second switches, then the second switch alone, and then neither switch, and return movement of the steering column serving to close the second switch alone, the second and first switches, the first switch alone and then neither switch, the second switch serving when it is closed to provide power to the bistable circuit provided that the flasher unit is coupled to the flasher lamp, and also serving to drive the bistable circuit to a first state, and closing of the first switch on return movement of the steering column while the second switch is still closed serving to drive the bistable circuit to its alternative state, the bistable circuit when in its alternative state providing an input to the latching mechanism. 

1. A direction indicator control circuit for a road vehicle, including a manually operable switch biased to an open position, an electromagnetic bistable latching mechanism which is operated when the switch is closed momentarily and serves to close a contact coupling a flasher unit to a flasher lamp, a further momentary closure of the switch serving to operate the latching mechanism again to open the contact, and means operable upon completion of a turn for operating the latching mechanism to open the contact.
 2. A circuit as claimed in claim 1 in which said means is magnetically operable.
 3. A circuit as claimed in claim 2 in which the magnetically operable means operates a bistable circuit which in turn operates the latching mechanism.
 4. A circuit as claimed in claim 3 in which the magnetically operable means includes first and second normally open switches operated by a permanent magnet on the steering column of the vehicle, movement of the steering column to negotiate a turn serving in sequence to close the first switch alone, then the first and second switches, then the second switch alone, and then neither switch, and return movement of the steering column serving to close the second switch alone, the second and first switches, the first switch alone and then neither switch, the second switch serving when it is closed to provide power to the bistable circuit provided that the flasher unit is coupled to the flasher lamp, and also serving to drive the bistable circuit to a first state, and closing of the first switch on return movement of the steering column while the second switch is still closed serving to drive the bistable circuit to its alternative state, the bistable circuit when in its alternative state providing an input to the latching mechanism. 